Figure 1.

A new pathway for the formation of disulfide bonds in the periplasm. In the normal pathway, disulfide bonds are introduced in reduced secreted proteins by DsbA. DsbA is then recycled by the inner-membrane protein DsbB, which is reoxidized by molecular oxygen in a ubiquinone- and cytochrome oxidase-dependent reaction. We recently developed a new pathway for disulfide bond formation: A thioredoxin mutant with a [2Fe-2S] cluster is exported from the cytoplasm to the periplasm where it can catalyze disulfide bond formation independently of the action of DsbA and DsbB.